The ring-closing metathesis (RCM) reaction has been shown to be a useful method for stabilizing the helical conformation and metabolic profile of peptides.  Earlier work from our groups suggested that it should be possible to synthesize 3₁₀-helical peptides containing a minimal RCM-derived cross link between amino acids separated by two residues, provided that each side chain contains at least five atoms.  To test this idea, short peptides (1a-e, 2a-c) composed of helicogenic amino acids (a-aminoisobutyric acid, Aib; C^a-methyl, C^a-bishomoallylglycine, hhMag) and containing pendant olefins at the i and i+3 positions have been prepared for the purpose of investigating (i) their RCM reactions and (ii) the structural effects of this modification.  We find that some of these systems undergo ring-closing reactions to yield exclusively the trans alkene product in good yield.  For certain systems, conditions have been identified that favor dimerization, which can arise from a tandem cross-metathesis/RCM reaction.  This presentation will summarize our synthetic and conformational studies.